Diruthenium Diacetate-Catalyzed Aerobic Oxidation of Hydroxylamines and Improved Chemoselectivity by Immobilization to Lysozyme

A new green method for the preparation of nitrones through the aerobic oxidation of the corresponding N,N-disubstituted hydroxylamines has been developed while exploring the catalytic activity of a diruthenium catalyst, i.e. [Ru2(OAc)4Cl]), in aqueous or alcoholic solution under mild reaction conditions (0.1 to 1 mol% catalyst, air, 50 °C) and reasonable reaction times. Notably, the catalytic activity of the dimetallic center is retained after its binding to the small protein lysozyme. Interestingly, this new artificial metalloenzyme conferred complete chemoselectivity to the oxidation of cyclic hydroxylamines, in contrast to the diruthenium catalyst.